1. Field of the Invention
This invention relates generally to a wheeled vehicle designed to turn about a central vertical axis. In particular, the invention relates to powered utility riding vehicles of the type useful for moving trailers about a trailer terminal, truck yard, or warehouse where rotation-in-place steering is advantageous.
2. Description of Prior Art
Within the transportation industry, semi-trailers are often routed through trailer distribution terminals or trailer yards. Space is normally at a premium resulting in limited maneuvering space within the yards. The trailers must often be shuttled about the yards and are typically moved using terminal tractors. Conventional terminal tractors, also known as trailer jockies or yard mules, typically resemble shortened road tractors. They are configured with two axles, one in front, the other in the rear. The rear axle is fixed to the frame of the vehicle and provides motive force via a pair of dual wheels. The front axle provides for vehicle steering via two steerable wheels which simultaneously pivot with a limited angular range.
A semi-trailer is pivotably coupled by a standard fifth wheel plate hitch located above the rear axle. Since there is a fixed distance between the fixed rear drive axle and the front steerable axle, a turning radius is required that far exceeds the space actually occupied by the vehicle itself. The longer the distance between front and rear axles, the larger the turning radius that is required to change directions of the vehicle. A large turning radius makes maneuvering around tight areas difficult and often dangerous. In a terminal where semi-trailers are frequently moved and space is constrained, a tractor with a small turn radius is advantageous. Because of their smaller lengths and turn radii, specialized terminal tractors are generally preferable to retired road tractors for use within terminals.
In a truck yard, an operator must often move in reverse to maneuver in tight spaces. Operators are required to look over their shoulders in order to back up. In a congested location, hazards from reversing are increased. Even with shortened terminal tractors, it is often difficult, even for a skilled operator, to park a semi-trailer against a wall in a slot or stall between two other trailers. In some instances, a backing maneuver cannot be accomplished without uncoupling the trailer, moving the tractor to a more favorable angle, and re-coupling the trailer to complete the move. In other instances, it may be necessary to jockey the trailer back and forth many times in order to back the trailer into a given stall.
It is also time consuming to back a conventional terminal tractor fifth wheel plate into engagement with the king pin of the trailer even with the V-shaped slot and the double-oscillation mount common with fifth wheel plates. Precision maneuvering is required while the driver must look backward resulting in operator fatigue and inefficiency. The driver must also exit the tractor cab in order to connect the air hoses and electrical cable to the trailer. The hitching operation is further complicated in the instances where a pintle hook/gudgeon hitch is used in place of the fifth wheel plate/king pin hitch.
In a truck yard where trailers are routinely coupled, moved, and then uncoupled, any increase in coupling efficiency, maneuvering efficiency, and safety amount to a significant cost savings. It is desirable, therefore, to have a vehicle with greater maneuverability and the ability to simplify the hitching process to enhance the safety of the operator and of the surroundings.
Prior art vehicles are known for turning with a zero turning radius, or so called “turning on the spot.” U.S. Pat. No. 3,938,608 describes a vehicle with a single center-mounted pivoting drive motor that is rotated about a vertical axis in order to change directions of the vehicle. The '608 vehicle is supported with three or more swivel wheels located at equal radial distances from the center wheel. The '608 outer profile is in the shape of a rectangle and has appendages that make close proximity maneuvering impossible next to another object such as a nearby trailer. Furthermore, the '608 vehicle lacks tractive force because of the single drive wheel. A single drive wheel must be rotated in order to change the vehicle direction, and although the single drive wheel can be turned to direct the vehicle in any direction, it does not provide directional stability for the case where a force is exerted on the vehicle from an angle to the line of intended travel. For example, a force against the '608 vehicle at a 20 degree angle to the right or left of the line of travel would force the single '608 wheel to skid, causing loss of directional control.
More recently, U.S. Pat. No. 6,581,703 describes an omni-directional vehicle which is round and which has a trolley adapted to rotatably mate with the vehicle and support a tow-bar. The '703 vehicle overcomes many limitations of the '608 vehicle, but the '703 vehicle is not adapted to couple to and support the weight of a loaded semi-trailer.
3. Identification of Objects of the Invention
A primary object of this invention is to provide a service vehicle which is designed and arranged for moving semi-trailers with enhanced maneuverability.
Another object of the invention is to provide a service vehicle that can turn on the spot and be of the smallest physical size relative to the space it occupies.
Another object of the invention is to provide a service vehicle which reduces the risk of accidents which may result in damage or injury to equipment or operating personnel.
Another object of the invention is to provide a service vehicle having an outer perimeter that defines an outer imaginary cylinder that encloses any equipment or appendages rigidly mounted on the vehicle thereby enhancing its capability to maneuver the vehicle without impacting objects external to the vehicle.
Another object of the invention is to provide a vehicle which expedites the process of hitching a trailer by allowing the driver to face the hitch assembly and trailer while positioning the vehicle to the trailer for coupling.
Another object of the invention is to provide a vehicle for moving semi-trailers from one location to another location which obviates the need for the operator to drive in a reverse direction.
Another object of the invention is to provide a vehicle that can push a trailer while providing an unobstructed view under the trailer for the driver to promote safe and efficient docking of the trailer.
Another object of the invention is to increase the operating efficiency of a semi-trailer terminal or truck yard by allowing a driver to connect and disconnect the primary and brake air hoses and electrical cable (pigtail) without having to dismount the tractor.